It is possible to have too much breast cancer awarenessby Michael Baum / June 20, 1997 / Leave a comment
In November last year British women were subjected to a breast cancer awareness month. Breast cancer was everywhere in the media, from broadsheet newspapers to soap operas. It even featured on the London underground with huge advertisements warning women that 1 in 12 would develop breast cancer in the course of their life. I was unsure what this publicity was meant to achieve and, judging from discussions with colleagues, who are also cancer specialists, no one of high rank had been consulted on the campaign. Most of us share the view that there is too much breast cancer awareness and and what we need, to give us a break from the excess of inappropriate referrals to our clinics, is a breast cancer unawareness month.
To describe the risk of developing breast cancer as 1 in 12 of the population is true, yet unhelpful. The 1 in 12 applies to a cumulative risk for those women who live to the age of 85. The incidence of breast cancer under the age of 30 is extremely rare and yet it is these women who are bombarded by breast cancer awareness campaigns and, as a result, grossly overestimate their risk. The real risk for women between the ages of 30 and 50 is about 1 per 1,000 per year. Under the age of 30 breast cancer is so rare it should not feature in a woman’s worst nightmares. Between the ages of 50 and 70 the time during which mammographic screening is often recommended, the risk rises to about 2 per 1,000 per year, and about a third of all reported breast cancers occur in the 70-85 age group.
If a woman finds out that she has a risk of breast cancer which is twice the average she is entitled to assume that she has a 1 in 6 chance of dying of the disease within the foreseeable future. Yet if she is 30 years old, her real risk doubles to 2 per 1,000 per year, which might seem insignificant against the other risks of living in a modern society.
Women with a family history of the breast cancer genes are different. These women have a 50 per cent chance of inheriting the gene. The gene itself has an 80 per cent penetrance, so these women know that they have a 40 per cent chance of developing breast cancer before the age of 60. Such women, if counselled, might make a rational decision to undergo prophylactic mastectomy, although this does not in itself offer absolute protection.
Despite recent scares, breast cancer mortality is identical in the long run between pill users and non-users, and if women are frightened off the pill there will be more morbidity and mortality associated with unwanted pregnancies than with carcinoma of the breast. Scares about hormone replacement therapy (HRT) are also tiresomely frequent. So frequent that I cannot help feeling that there is some ill-advised feminist lobby at work which believes that HRT is “unnatural” and should be discouraged. What is natural? Judging by Victorian England or the third world today, women become dried out husks through childbearing before the menopause. It is one of the triumphs of modern medicine that most women can live happy, healthy lives beyond the menopause.
Even if it does bring a small increase in breast cancer risk, HRT improves the quality of life and reduces the risk of ischaemic heart disease and osteoporosis. A harm-benefit analysis always ends up in favour of HRT. But I wonder how many women with a family history of osteoporosis and ischaemic heart disease have their lives shortened because of irrational fear of HRT?
There is much evidence to suggest that tamoxifen might prevent breast cancer among women at risk. We know with confidence that five years of tamoxifen will reduce the risk of a contralateral breast cancer by about 50 per cent. As a spin off from trials we have also learnt that tamoxifen may modestly reduce ischaemic heart disease and osteoporosis but increase the incidence of endometrial cancer. But if tamoxifen can prevent 50 per cent of breast cancer incidence then for every 1,000 women treated ten fewer would die, against a worst estimate of one extra death from endometrial cancer. It is surely rational on harm-benefit grounds to continue trials.
What about screening? Women are told that screening will reduce the risk of dying of breast cancer by 25 per cent. Yet how many women appreciate what this means. Take a woman of 50 who is screened three times between the age of 50 and 59: during that time there would be a 2 per cent risk of developing breast cancer and at worst a 1 per cent risk of dying. The risk reduction is 25 per cent of 1 per cent which is 0.25 per cent-in other words 99.75 per cent of women will achieve no benefit and be exposed to potential harm. I do not mean radiation, but the false alarms, unnecessary biopsies, overdiagnosis of duct carcinoma in situ, psychological damage and problems with life assurance applications. I am not saying that screening should be abandoned but there are opportunity costs which have been incurred by the single minded pursuit of the screening option.
A study in the Journal of the National Cancer Institute in 1995 found that women in New York overestimated their risk of dying of breast cancer within the next ten years on average by 22 fold and as a result overestimated the benefits of screening 127 fold. We need to re-educate the public about risk but before we can do so we have to re-educate the profession.